The present invention relates to a drying device with thermal management comprising a titano-alumino-phosphate as adsorbent for energy-improved drying of objects and appliances, and its production.
The present invention further relates to a method for removing residual moisture from objects and appliances, as well as a method for regenerating a water-containing titano-alumino-phosphate.
Microporous structures such as zeolites which also include alumino-phosphates (APO), silico-alumino-phosphates (SAPO), titano-alumino-phosphates (TAPO) or titano-silico-alumino-phosphates form a structurally diverse family of silicate minerals with complex structures. They occur naturally but are also manufactured synthetically. The minerals of this group, depending on the structure type, can store up to 40 per cent of their dry weight as water which is released again when they are heated to 350 to 400° C. Through the regeneration, material is obtained which can be used again for drying.
However, it is not only alumino-silicate zeolites that display structural diversity and good adsorptivity, but also the group of alumino-phosphates. Structures of this group are classified by the “Structure Commission of the International Zeolite Association” on the basis of their pore sizes according to IUPAC rules (International Union of Pure and Applied Chemistry). As microporous compounds they have pore sizes of 0.3 nm to 0.8 nm. The crystal structure and thus the size of the pores and channels formed is controlled by synthesis parameters such as pH, pressure and temperature. Further factors such as the use of templates during synthesis, as well as the Al/P/Ti/(Si) ratio, also determine the resulting porosity. They crystallize into more than two hundred different variants, into more than two dozen different structures, which have different pores, channels and cavities.
Because of the balanced number of aluminum and phosphorus atoms, titano-alumino-phosphates are neutral in charge. Titano-silico-alumino-phosphates (TAPSO) form as a result of the isomorphic exchange of phosphorus with silicon. As a result of the exchange, surplus negative charges form which are balanced by the insertion of additional cations into the pore and channel system. The level of phosphorus-silicon substitution thus determines the number of cations required for balancing, and thus the maximum charging of the compound with positively charged cations, e.g. hydrogen or metal ions. As a result of the insertion of the cations the properties of the titano-silico-alumino-phosphates (TAPSO) can be set and modified.
The framework structures of the titano-alumino-phosphates are constructed from regular, three-dimensional spatial networks with characteristic pores and channels which can be linked with each other in one, two or three dimensions.
The above-mentioned structures are formed from corner-connected tetrahedral units (AlO4, PO4, TiO4, optionally SiO4), each consisting of aluminum and phosphorus, as well as optionally silicon, tetracoordinated by oxygen. The tetrahedra are called the primary structural units the connecting of which results in the formation of secondary structural units.
Titano-alumino-phosphates, silico-alumino-phosphates and titano-silico-alumino-phosphates are usually obtained by means of hydrothermal synthesis starting from reactive gels, or the individual Ti, Al, P, and optionally Si components obtained which are used in stoichiometric ratios. Titano-alumino-silico-phosphates (TAPSO) are produced analogously to silico-alumino-phosphates (SAPO) (DE 102009034850.6). The latter can be obtained crystalline by adding structure-directing templates, crystallization nuclei or elements (e.g. EP 161488).
Titano-alumino-phosphates are used primarily as catalysts in MTO (methanol-to-olefin conversion) processes in which, starting from methanol, a mixture of ethene and propene can be obtained with the aid of specific microporous catalysts.
Alumino-phosphates are popularly used in dehydration reactions (EP 2 022 565 A1) due to their good hygroscopic properties and their high adsorption power.
The adsorption power of the titano-silico-alumino-phosphates is particularly good due to the microporous framework structure. Titano-alumino-phosphates also display good adsorption behaviour as a large number of molecules can be adsorbed on the large surface area. If water molecules strike the surface of the titano-alumino-phosphate, they are adsorbed. An exothermal accumulation takes place on the surface, accompanied by the release of the kinetic energy of the water molecules as well as their adsorption energy which is released in the form of adsorption heat. The adsorption is reversible, wherein desorption represents the reverse process. In general, adsorption and desorption are present in a concurrent equilibrium which can be controlled and influenced by temperature and pressure.
Due to their low toxicity and their ease of handling, zeolites are already used for drying in various areas of everyday life.
Zeolites are known from the state of the art due to their hygroscopic properties. They are used for drying solutions or for dehumidifying closed spaces, as well as for drying textiles after a washing process or dishes in dishwashers.
Zeolites support the drying of textiles as they are usually dried at low temperatures and with minimal movement of the damp textiles. Temperatures that are too high can cause sensitive fabrics to shrink and become unusable. Alternatively, the drying process can be carried out statically, as a result of which however the drying period is increased as the water contained in the textiles can only be withdrawn from the surface.
The drying of dishes in dishwashers is ideally to be as uniform as possible, as otherwise undesired water spots can form. In particular in catering and at home, this leads to unsatisfactory visual results and often necessitates subsequent work on dishes, glasses and cutlery.
It is therefore attempted to optimize the drying process, e.g. by using better dishwashing detergent with pearlescent effect or removing more water from the textiles, already in the washing machine, which can be achieved by higher rotation speeds during spinning. However, the latter cannot be increased infinitely. Increasing the rotation speeds leads to a more pronounced stress on the material of the washing machine, to greater noise development as well as to the loss by textiles of their shape and elasticity as a result of over-vigorous spinning.
Various standard methods for drying objects and appliances are known from the state of the art. Textiles are usually dried by means of heated air streams accompanied by continuous movement.
WO 2009/010446 discloses an adsorption dryer which is used for drying textiles using below-atmospheric pressure and a heating device. A zeolite is additionally used as adsorbent for improving the drying effect. The additional use of a zeolite as adsorbent for removing moisture from textiles makes possible a more rapid drying of the textiles. However, this is associated with a higher energy outlay. To regenerate the water-containing zeolite, the latter must be heated, resulting in additional energy costs. The desorption of water from the framework structure of the zeolite is then carried out by a prolonged treatment at high temperatures of from 250° C. to 400° C.
Zeolites can also be used in dishwashers for the improved drying of dishes (DE 20 2208 011 159 U1). To regenerate the water-containing zeolite accompanied by desorption of the adsorbed water, a treatment at high temperatures (250° C. to 400° C.) is required which results in additional energy costs.
Despite the advantage that the drying times for dishes and textiles are shorter, it is disadvantageous that a lot of energy must be expended for each drying process. Although the drying effect is increased by the use of zeolites, the energy-intensive regeneration of the water-containing zeolite results in higher electricity costs. This is an undesired side-effect which is particularly undesirable at a time when energy efficiency is paramount.
Thus no energy-efficient drying devices or methods are known from the state of the art which make possible a low-energy and low-cost, as well as efficient, uniform and gentle drying of objects and appliances. The energy-efficient regeneration of the adsorbent for desorption of the adsorbed water represents a particular problem the solution to which is to date not known from the state of the art.